A throttle apparatus of dual cable/electronic control type, and a throttle apparatus of single electronic control type have been known as conventional throttle apparatuses applied to engines installed on four-wheeled vehicles.
For example, on an intake system provided with two surge tanks which are used to combine each three intake passages corresponding to respective cylinders on a V-type six-cylinder engine, and intake passages extending upstream from the respective surge tanks, the conventional dual cable/electronic-controlled throttle apparatus interlocks two throttle valves with each other, which are disposed in the respective upstream intake passages, by means of a single throttle shaft, thereby driving the throttle valves to be opened/closed by means of a cable or a motor (refer to patent document 1, for example).
The conventional electronic-controlled throttle apparatus rotatably combines throttle valves, which are disposed respectively in two intake passages formed on throttle body, by means of a single throttle shaft, thereby driving the throttle valves to be opened/closed by means of a motor disposed on one end of the throttle shaft (refer to patent document 2, for example).
The above-mentioned conventional apparatuses are disposed upstream of the surge tanks or upstream of the relatively long intake passages, and the intake air controlled by the opening/closing action of the throttle valves is thus once accumulated in the surge tanks, and is then flowed through the intake passages corresponding to the respective cylinders. Thus, a change in the intake air quantity due to a small variation of the opening/closing operations of the throttle valves, a displacement from the synchronization of the two throttle valves, and the like do not pose serious problems.
On the other hand, as throttle apparatuses for engines installed on two-wheeled vehicles and the like, due to the responsiveness to a throttle operation being emphasized, there has been known a multi-throttle apparatus where throttle valves are disposed respectively in intake passages corresponding to the respective cylinders (intake ports) at a location close to the intake port of a cylinder head, throttle shafts rotatably supporting the respective throttle valves are connected by a synchronization lever, an energizing spring, and the like used for a transmission of the torque, and a single cable is used to drive all the throttle valves to be opened/closed. In addition, on this apparatus, an independent ISC valve is provided to carry out idle speed control (ISC) of the engine.
[Patent Document 1]
Japanese Laid-Open Patent Publication (Kokai) No. H6-207535
[Patent Document 2]
Japanese Laid-Open Patent Publication (Kokai) No. H8-218904
It has been studied to provide electronic control which drives multiple throttle valves by means of a motor, and further, control of the idle speed by finely adjusting the opening/closing angle of the throttle valves without an independent ISC valve also on engines installed on two-wheeled vehicles and the like. In addition, the throttle operation on the two-wheeled vehicles is more sensitive than that on four-wheeled vehicles, and is accompanied by rapid changes, and there are thus required a precision in the synchronization corresponding to the sensitivity, high responsiveness following the rapid changes, and the like.
If the above-mentioned conventional throttle apparatuses for four-wheeled vehicles are applied as a throttle apparatus for two-wheeled vehicle and the like, the responsiveness is inferior, and the practicality lacks. Namely, on these apparatuses, a middle portion of the throttle shaft is directly supported by through holes on the throttle bodies or brackets, the friction resistance is thus large on sliding parts, and due to influence of a resistive force of the intake air received by the throttle valves caused by the rapid change, the moment of inertia of the throttle valves, and the like, the throttle shaft may be brought in close contact with the through holes to generate a stick and the like, or the throttle shaft may generate a torsion to cause mutual displacements from the synchronization among the throttle valves and the like.
In addition, if a motor is simply installed on the conventional multi-throttle apparatus for two-wheeled vehicles, and electronic control is intended while the rotation angle of the throttle shaft is used as a control parameter, mutual slight displacements from the synchronization (phase shift) among the throttle valves and the like, which are permitted in the conventional cable control, cause obstruction in the realization of the electronic control. Especially, it is necessary to surely prevent the displacement from the synchronization for the control in the case of carrying out the idle speed control by means of the throttle valves without the ISC valve.
The present invention is devised in view of the problems of the above-mentioned prior art, and has an object of providing a multi-throttle apparatus which, upon driving multiple throttle valves respectively disposed in intake passages to be opened/closed by the motor, is excellent in responsiveness to rapid changes while synchronizing the respective throttle valves, integrates components, reduces the size, and is preferable for high-performance engines installed especially on two-wheeled vehicles and the like.